Since its discovery in 1999, three methods have been used to make Fe16N2. In a first method, flowing ammonia gas (NH3) over iron powder in a furnace converts the iron powder into Fe16N. Furnace conditions include temperatures between 120-210° C. for 3 to 200 hours at atmospheric pressure. This method, however, releases significant amounts of ammonia gas into the environment.
In a second method to make Fe16N2, a furnace heats iron powder in a flowing gas mixture of H2 and NH3 to form iron or an iron nitride. Continued heating to temperatures above 600° C. transforms the material into γ iron nitride. Quenching of the γ iron nitride in an ice bath or liquid nitrogen forms α′ iron nitride. Heating of the α′ iron nitride to temperatures below 200° C. forms Fe16N2. Both of the methods described above release ammonia gas into the atmosphere. Furthermore, both methods suffer from low penetration of the ammonia gas into the iron powder. This wastes a significant portion of the ammonia gas and results in low amounts of iron powder transforming into Fe16N2. Methods to reclaim the flowing ammonia gas are known, but require additional cost and equipment such as cooling/condensation chambers attached to the furnace.
In a third method, sputtering or ion implantation forms a thin film of Fe16N2. In addition to suffering from low throughput, it produces a thin film that is difficult to process into coatings or desired shapes.
These conventional methods suffer from an inability to efficiently produce bulk amounts of Fe16N2 and can require costly additional steps to reduce the environmental impact of using flowing ammonia gas. Thus, a need exists in the industry to address the aforementioned deficiencies and inadequacies.